The present invention relates to apparatuses for removing spilled oil from the surfaces of water bodies, and more particularly to apparatuses and methods for removing oil using drum skimmers.
When oil is spilled into a water body, such as from a damaged oil tanker, the spilled oil forms a thin film on the surface of the water body. This film is sometimes referred to as an oil slick or sheen. Oil films are detrimental to the marine environment, and will damage shorelines if allowed to drift ashore. The following is a summary of the many different apparatuses and methods have been developed for collecting spilled oil from the surface of water bodies.
The closest known prior art is U.S. Pat. No. 5,030,363 (Pole), which differs significantly from the present invention. Pole describes an oil retrieving vessel having a cylindrically shaped collection surface. Preferably, the cylindrically shaped collecting surface is a drum having closed ends. The drum is preferably watertight and is light weight so that it is buoyant enough to float on the oil alone or on the oil and water. The drum moves up and down with the waves on the water independently of the rest of the vessel. (Col. 3, lines 27-35). Pole mentions that the drum can be set in a fixed vertical position relative to the pontoons, and further mentions that if an open ended drum is used, it can be made of lightweight durable material that will float. (Col. 9, lines 38-42). Pole does not explain how a drum having open ends would be mounted on the vessel. Pole does not teach scrapping of a central baffle or the use of a unitary vessel having an incorporated oil collection tank fixed therein. Nor does Pole suggest that the interior of a hollow cylinder could be scraped. Pole does not disclose a unitary vessel. Rather, Pole discloses a pair of pontoons joined together by cross-members. (Col. 4, lines 5-11). The oil collection tank is separate from the pontoon system, and is changed as needed. (Co. 4, lines 16-30, 58-63). Oil scraped from the outer surface of the drum is diverted directly into a forward end of the separate oil collection tank. (FIG. 3)
The only known prior art that teaches scraping from inner and outer surfaces of a cylinder is U.S. Pat. No. 2,242,861 (Keene). However, Keene relates to an entirely different field of art, namely the filtering of solid matter from a liquid. (Col. 1, lines 1-5). The device of Keene is used in a tank of liquid. Nothing in Keene suggests that the device could be adapted for use on a hull of a floating vessel.
U.S. Pat. No. 5,618,420 (Stella) and U.S. Pat. No. 5,522,990 (Davidian) disclose scraper collection of oil from opposite sides of rotating members, e.g. conveyor belts and rotating disks. U.S. Pat. No. 4,100,072 (Uchida) and U.S. Pat. No. 3,968,041 (De Voss) disclose the use of conveyor drums and conveyor belts for lifting oil from the surface of the body of water.
The use of rotating drums as a means of collecting oil from a surface of a water body is well known. See U.S. Pat. No. 4,173,536 (McCall) (FIG. 4 near element 34), U.S. Pat. No. 3,576,257 (Yates) (element 50), U.S. Pat. No. 5,380,431 (Newsom) (FIG. 11 element 40 or element that is perpendicular to element 42 in FIG. 2).
U.S. Pat. No. 4,013,561 (Murphy), U.S. Pat. No. 3,947,360 (Fast), and U.S. Pat. No. 3,838,775 (Larsson) show roughening the texture of an oil collection drum in order to improve adherence of oil.
An example of an early patent that relates to a method for the separation of oil and water from an emulsion is shown in U.S. Pat. No. 3,685,653. The ""653 patent relates to the facilitating and expediting of separation of oil/water emulsions by passing the emulsion as a surface film on a rotating pick up roller into a bight formed by a closely spaced parallel roller arrangement to coalesce the oil particles, break up the emulsion and liberate free oil.
A system for removing floating oil from water is shown in U.S. Pat. No. 3,850,807 issued to Loyd Jones. The invention relates to water pollution control and especially concerns a system for removing dispersed oil from a floating inland stream. A bed of granular sulfur is provided within a unique container buoyantly supported by the stream. In most oily streams the oil, due to gravity, accumulates on the surface in a very thin film, sometimes referred to as an oil slick or sheen. This top portion of the stream is directed through the bed of granular sulfur where the oil is coalesced and removed, leaving clean water flowing from the container.
The Ayers, et al, Pat. No. 3,959,136 relates to a method and apparatus for removing oil from a surface of a body of water with a skimmer, the apparatus including a skimmer with baffled entry ports arranged on a plane inclined to the direction of current flow or about the periphery of a drum so that oil enters through the baffles into a chamber which is beneath an inverted funnel or within the axle of the drum; the method involving providing a skimmer having submerged baffle entry ports inclined to the direction of a current flow, allowing the oil to enter the skimmer, and returning the skimmer to a horizontal position for removal of the oil therefrom through an inverted funnel suspended over the confined oil.
A method and apparatus for pollutant spill control is disclosed in U.S. Pat. No. 4,234,420. The apparatus includes an aquatic vessel comprising a buoyant storage tank, a rotatable cylinder mounted on the tank normal to the relative flow of the aquatic body, a plurality of magnetic bands mounted circularly about the drum and parallel relation.
The Morris Pat. No. 4,360,429 discloses an apparatus for recovering fluids floating on a body of water. The apparatus comprises a support structure and two rows of discs mounted on the support structure so that the discs are in contact with the fluid. The discs of each row are spaced-apart coaxially along a shaft. There is a motor coupled to the shafts for rotating the shafts and the discs. Wipers contact the sides of the discs for wiping the fluid from the discs as the discs rotate and collect the fluid. The shafts are parallel and spaced-apart a distance such that the discs of the two rows interdigitate.
The Wylie Pat. No. 4,510,054 relates to an oil spill recovery method and apparatus. The method of recovery involves the pumping of an oil/water mixture from a concentration area to a submerged portion of a vertically oriented cylinder, open at both ends, and the separation of the oil from the water in the cylinder. Oil floats to and accumulates on the surface of the water in the cylinder and uncontaminated water flows out through the lower open end of the cylinder. The apparatus includes a collection unit which defines the concentration area within three walls thereof, a recovery unit which follows the collection unit and mounts the cylinder therein, and a submerged pumping unit which carries an oil/water mixture from the concentration area in the collection unit to the cylinder in the recovery unit. There is very little emulsification of the oil in the cylinder and hence there is very efficient separation of the oil from the water.
An apparatus for recovery of oils or other similar pollutants floating on bodies of water is disclosed in the Ayroldi Pat. No. 4,514,299. The recovery unit includes two large rotating horizontal axis drums surrounded on the lateral and the rear sides of an apron to contain the floating oils, and is towed by a support vessel to float independently.
An oil recovery vessel is the subject of U.S. Pat. No. 5,047,156. The vessel admits oily water through bow openings to sluiceway and an adjustable height weir for skimming oil, debris and other pollutants from the sea water.
U.S. Pat. No. 5,049,287 discloses an oil spill recovery method and apparatus.
U.S. Pat. No. 5,314,618 discloses a single drum skimmer and weir skimmer for recovering all types of oil from the surface of a body of water. An aluminum high density polyethylene lined drum, floated by adjustable pontoons is rotated clockwise by a hydraulic drive motor, thus drawing the oil layer on top of the water, under and over the drum to a high density polyethylene scraper blade where it is scraped off into a collection box. The oil runs to the corners of a collection box where it is suctioned off through suction hoses to a camlock xe2x80x9cteexe2x80x9d fitting. The oil travels through a main suction hose to a peristaltic master pump which provides suction and discharge of oil from the skimmer to a vacuum dehydrator. An open topped, adjustable reservoir/weir collector has an opening in the front panel which may be opened for weir skimming, and closed for drum skimming.
U.S. Pat. No. 5,380,431 provides an oil recovery system for recovering oil spilled upon a body of water. Oil accumulators having numerous open ended cells that entrain spilled oil upon the surfaces of the cells when partially submerged in an area where oil has been spilled upon water. The oil accumulators are rotated so as to lift the oil entrained upon the cell surfaces from the water. An oil remover may have super heated steam nozzles located immediately above the oil accumulator. When oil-bearing cells pass beneath the nozzles, super heated steam may warm and expel the oil from the cells. An oil collector collects the oil removed by the oil remover where gravity flow transports the oil to a storage reservoir.
U.S. Pat. No. 5,609,755 provides an apparatus that takes advantage of the adherence of hydrocarbonates to specific material and its fluidity as influenced by the temperature. The performances of the apparatus are related to the interaction of two horizontal concentric cylinders one rotating around the other and containing both collecting and recovery means, working simultaneously. A three way oil collection is achieved by the cylinder""s exterior surfaces, by large conical discs and by oil scoops located between the two cylinders. Said collecting means are integrated with a central heating system and with temperature controlled recovery devices such as oil deflectors with scrapers and oil recovery reservoir with screw, so that any type of oil can be recovered efficiently from or near the water surface even in cold weather.
U.S. Pat. No. 5,685,979 discloses an oil skimming device that includes a pair of hulls between which is suspended a skimmer box containing a plurality of oleophilic discs. The skimmer box has an outwardly opening bottom door which promotes a draft of water through the skimmer box when the device is in forward motion. Alternately the device can be operated in a stationary mode wherein water is evacuated from the skimmer box by means of a stand pipe inside the box. The skimmer box and oleophilic disc array are demountable and the pair of hulls can be folded together for transportation.
U.S. Pat. No. 5,522,990 discloses an oil removal device for separating floating oils from water or water-based liquids. A rotating disk lifts viscous oils from the water or water-based liquid. The oil is removed from the side by wiper blades on either side of the disk on the downward part of the disk""s travel. The oil then falls into channels and is channeled into a storage container. A support frame comprising a base and a center post attached to the base is connected to and supports the disk, wiper blades and channels. A gravity separating chamber could be used in place of the storage container. Water collected by the disk is diverted from the oil by a small scale gravity separator module. The gravity separator module includes a weir having a gap or space at the bottom to separate the water from the oil.
U.S. Pat. No. 2,242,861 discloses a rotary filter, a rotary drum-type filer wherein the drum carries a filter media and rotates within a tank containing the liquor from which solid matter is to be separated. The drum consists of a cylindrical shell on the periphery of which is formed an annular compartment by the super position of a filter cloth or other filter medium. The cloth is virtually is in the form of an endless band which is supported annularly drum shell by suitable means and the annular chamber so formed and in some cases is divided into a number of smaller compartments. Scraper blades on both the inside and outside of the drum are employed to remove the precipitate from the outer face of the rotor and from the inner face of the rotor.
Although many efforts have been made to provide efficient and effective surface oil collection devices, many of these devices have had only limited success. There thus remains a need for an oil skimming apparatus that meets the following objects and has the following characteristics.
It is an object of the invention to provide an oil skimming apparatus that offers significantly improved oil collection rates and efficiencies over the prior art.
It is an object of the invention to provide an oil skimming apparatus that provides for collection of oil from the outer and inner surfaces of a hollow, non-floating cylinder.
It is another object of the invention to provide a scraper type oil skimming apparatus that facilitates replacement of scraper blades.
It is another object of the invention to provide an oil skimming apparatus that can operate efficiently in high currents.
It is yet another object of the invention to provide an oil skimming apparatus that can operate efficiently in rough sea states and in other hazardous conditions.
It is still another object of the invention to provide an oil skimming apparatus that can be used for coastal, offshore, and oil pit separators.
These and other objects and advantages of the invention shall become apparent from the following general and preferred description of the invention.
Accordingly, an oil skimming apparatus for collecting oil from a surface of a water body is provided comprising, generally, a floatable hull, a hollow cylinder rotatably mounted adjacent a bow of the hull, and an arrangement of scrapers and troughs for scraping oil from the inner and outer surfaces of the cylinder and transporting the collected oil to an oil collection tank. The oil collection tank is preferably fixed within the hull. A suction outlet is preferably provided for use in pumping collected oil from the oil collection tank. The cylinder has port and starboard open ends and a density greater than water. Because the cylinder has open ends and a density greater than water, it cannot float on a surface of a water body without external support. The cylinder also has at least a pair of bulkheads, namely a port bulkhead and a starboard bulkhead. The bulkheads are fixed in spaced apart relation within the cylinder. The bulkheads are preferably spaced about 30 cm apart. Spacing the bulkheads apart provides greater support for a drive shaft (described below). However, if the bulkheads are spaced too far apart, less inner surface is available for collection of oil, decreasing oil collection recovery. The cylinder is also preferably provided with an annular shoulder depending inward from each of the open ends of the cylinder. The annular shoulders of the cylinder are preferably wiped of oil by the inner scraper blades during use.
A pair of pontoons, namely a port and starboard pontoon, extend fore of the bow of the floatable hull. The pontoons are spaced apart to form an oil collection area. The cylinder is rotatably mounted in the oil collection area via a drive shaft-member passing through the port and starboard bulkheads. A lengthwise annular collar preferably passes through the pair of bulkheads to provide further support for the drive shaft. The drive shaft passes through the annular collar. The drive shaft preferably has an outer diameter of about 4 to 6 inches (10 to 15 cm) to thereby increase the strength and rigidity of the drive shaft. A rotational axis of the cylinder is aligned substantially parallel to the surface of the water body and substantially perpendicular to a centerline of the floatable hull. Additionally, a bottom edge of the open ended cylinder is positioned below a waterline of the floatable hull, such that oil and water on the surface of the water body spill into the interior of the cylinder. A drive means is provided for selectively rotating the drive shaft.
A series of oil collection troughs and scraper blades are arranged inside and outside of the cylinder to permit collection of oil from the cylinder. An outer oil collection trough is mounted along a fore outer surface of the cylinder. An outer scraper blade is positioned to scrape oil from the fore outer surface of the cylinder and to divert the scraped oil into the outer oil collection trough. A port inner oil collection trough is mounted along a fore inner surface of the cylinder between the port bulkhead and the port open end. A port inner scraper blade is positioned to scrape oil from the fore inner surface of the cylinder and to divert the scraped oil into the port inner oil collection trough. Similarly, on the other side of the vessel, a starboard inner oil collection trough is mounted along the fore inner surface of the cylinder between the starboard bulkhead and the starboard open end. A starboard inner scraper blade is positioned to scrape oil from the fore inner surface of the cylinder and to divert the scraped oil into the starboard inner oil collection trough. Because oil also collects on the internal bulkheads of the cylinder, a port bulkhead scraper blade can be positioned to scrape oil from the port bulkhead and to divert the scraped oil into the port inner oil collection trough. Likewise, a starboard bulkhead scraper blade can be positioned to scrape oil from the starboard bulkhead and to divert the scraped oil into the starboard inner oil collection trough.
A port oil transfer trough is positioned and configured to transfer oil from the outer oil collection trough and the port inner collection trough to the oil collection tank. Similarly, a starboard oil transfer trough is positioned and configured to transfer oil from the outer oil collection trough and the starboard inner collection trough to the oil collection tank. A valve is preferably provided in each of the oil transfer troughs for selectively shutting off flow of collected oil to the collection tank. The oil collection troughs preferably decline outboard and the oil transfer troughs preferably decline aft to thereby facilitate flow of collected oil to the oil collection tank. During collection of oil, solid debris can clog up the troughs, causing oil to spill out rather than drain into the oil collection tank. Accordingly, in a preferred embodiment the port and the starboard oil transfer troughs are recessed below a deck of the pontoons and the hull, such that the deck prevents solid debris from falling into the troughs.
The scraper blades preferably consist of ultra high molecular weight plastic (xe2x80x9cUHMWxe2x80x9d), but can alternatively be made of rubber, plastic, or other semi-rigid durable materials. Each of the scraper blades is preferably set at an angle of between 10 to 70 degrees relative to the surface of the body of water. In a most preferred embodiment, the scraper blades are set at an angle of between 45 to 55 degrees relative to the surface of the body of water. The various scrapers can be set at different angles from one another.
Another objective of the invention is to facilitate the changing of scraper blades, which tend to wear out during use and thus require replacement. The port and starboard oil transfer troughs are preferably positioned substantially level with the rotational axis of the cylinder, to thereby facilitate changing of scraper blades by providing a relatively large opening between the transfer troughs and a top edge of the cylinder. The port and starboard transfer troughs can be placed above the rotational axis of the cylinder without affecting the amount of oil collected; however, if the troughs are placed too close to the top of the cylinder, it becomes necessary to remove the troughs in order to change the wiper blades, which can cost several days of down time. To further facilitate access for changing of scraper blades, the cylinder can be provided with an inner diameter of three to six feet or more. A larger cylinder also allows the apparatus of the invention to collect oil in high sea states. The inner and outer surfaces of the cylinder preferably have a scratch surface to thereby improve adhesion of oil to the surfaces.
Such devices are often used in rivers and inland channels, where underwater hazards can puncture a hull can cause leakage of collected oil. Accordingly, the hull preferably has a double bottom to thereby prevent leakage of oil from the collection tank. The device is preferably built from high-grade aluminum.
The apparatus can also be provided with a cylinder cover pivotally connected to a deck of the hull adjacent the oil collection area. The cylinder cover is positioned and configured to cover the cylinder when pivoted to a closed position to thereby protect the cylinder, and to provide access to the cylinder when pivoted to an open position to thereby facilitate cleaning and maintenance of the cylinder. A front screen is preferably mounted fore the cylinder to thereby prevent trash from getting on the cylinder.
In a preferred embodiment, the hull has a tapered bow. The tapered bow is separated from the oil collection tank via an internal bulkhead. The internal bulkhead prevents oil from collecting in the tapered bow, which prevents the hull from listing forward during collection of oil.